Valve actuating trip means



March 26, 1963 R. H. YEO ETAL 3,082,627

VALVE ACTUATING TRIP MEANS Filed Sept. 19. 1960 2 Sheets-Sheet 2 ,A@Emiliani llfllllll/lfllllll/llllllvlllllllll/lll/l/l'/ f INVENTOR.

BY Enel J. CouLsoN JR.

Flr-ro Nsvs.

Rogier H. 4Viso mvp ite Stats This invention relates to a valve andvalve operating mechanism `by which the valve can be manually opened andclosed as long as an associated electric circuit is energized, and whichin the event of the failure of the electric circuit will automaticallyclose the valve and become inoperative to reopen the valve until theelectric circuit is re-established.

Many units of industrial equipment require for normal operation both theow of a fluid and the concurrent existence of an electric circuit suchas the circuit of a llame-sensing device, a temperature or pressurelimiting device, or other safety device, or the circuit of an electricmotor for driving some element of the equipment. For example, in thecase of an oil or gas furnace, the ow of the oil or gas fuel is normallycontrolled by some safety device and may be accompanied by the operationof an electric motor which drives some related element, for example, ablower to provide combustion air or a blower or pump for the fuel orsome other fluid. In many such cases, it is essential for safety thatthe flow of gas or oil should be immediately shut olf in the event ofopening of the safety circuit or of failure of the electric circuitsupplythe electric motor.

It is the object of our invention to provide a uidcontrol valve andvalve-operating mechanism which under normal conditions, that is, whilean associated electrical circuit is energized, will permit the valve tobe manually opened and closed, and will hold the valve open as long assuch normal conditions prevail, and which in the event of failure of theassociated electric circuit will automatically close the valve andrender itself inoperative to open the valve until the electric circuithas been re-established. It is a further object of the invention toprovide such a valve operating mechanism which is of improved, simple,and eifective construction. It is a further object of the invention tocombine such a mechanism with a signal device which will indicate,either locally or at a distance, the condition of the valve.

In accordance with the invention, an axially reciprocablevalve-operating rod is biased to valve-closing position and is arrangedto lbe moved to open position by pivotal movement of a lever linked to amanually operable crank arm. The lever is preferably a lever of thethird class, that is, a lever in which the fulcrum is at one. end, thevalve-actuating rod is connected at the other end, and the manuallyoperable crank arm is linked to an intermediate point, desirably a pointcloser to the valve operating rod than to the fulcrum. The fulcrumsupport for lever desirably consists of a pivoted rocker which carries afulcrum stool, and such support is normally unstable and incapable ofsupporting the lever and is held in fulcrum-supporting position by anelectromagnetic device energized by or with the associated electriccircuit. the event such circuit is de-energized, the fulcrum stoolcollapses or moves out from under the lever and permits the fulcrumedend of the lever to drop, thus releasing the valve rod for movement tovalve-closed position under the inuence of its bias to that position.When the electrical circuit is re-established, the electromagneticdevice will again hold the fulcrum stool in lever-supporting position,and by movement of the manually operable handle to latching or resetposition, the lever will return to its nor- 3,082,527 Patented Mar. 26,1953 mal operating relationship ready for pivotal Valve opening movementabout the fulcrum stool.

Desirably, the valve operating rod actuates an indicating plate which isexposed through a window when the valve is open and which is moved awayfrom the window when the valve is closed. A switch actuating arm may becarried with such indicating plate, to actuate a switch for operating aremote signal mechanism for indicating the condition of the valve.

The valve operating mechanism is desirably housed in Y a casing havingan open side, and having a partition wall Inl forming an electricaljunction box opening to the same side ot' the casing; and a single coverplate closes the open sides of both the casing and the junction box.

These and other objects and features of the invention are illustrated inthe embodiment shown in the drawings and more fully described below.

The accompanying drawings illustrate the invention. In such drawings:

FIG. l is a front elevation of a valve and valve operating mechanismembodying the invention, with parts broken away to show the valvestructure and the valve operating mechanism, the full-line showing beingwith the valve in closed position and the lever and fulcrum in latchposition;

FIG. 2 is a view' similar to FIG. 1 but with the full V lines showingthe parts in valve-open position;

FIG. 3 is a partial section similar to FIGS. l and 2, but showing theposition of the electromagnetic armature and the fulcrum stool when theelectrical circuit is interrupted;

FIG. 4 is a partial section taken on the line 4 4 of FIG. 1, showing thefulcrum stool and electromagnetic device in front elevation;

FIG. 5 is a horizontal section showing the Valve operating mechanism intop elevation with the parts in the positions shown in FIG. 2;

FIG. 6 is an end elevation of the valve mechanism shown in FIG. l, withparts broken away to show the indicator mechanism;

FIG. 7 is a front elevation of the manually operable valve handle andits indicating dial and stop mechanism; and

FIG. 8 is a diagrammatic side elevation of the fulcrum support, on anenlarged scale.

The device shown in FIG. 1 comprises a valve body 10 having an inletport 12 and :an outlet port 14, land containing .a pair of valve seatingrings 16 and 18 bearing against the sides of a valve gate 20 which isvertically movable -between the upper closed position shown and alowered position which brings a valve opening 22 into registry with theopenings through the seating rings 16 and 18. The seat ring 16 is sealedto the valve body 10, as by an O-ring, and `the seat ring 18 is springpressed Iagainst the face of the valve plate, `as by a spring washer 24.The upper end of the valve body carries `a rect-angular mounting plate26 closed by a cover plate 28 through which .the valve operating rod 30`is slidably movable and in which such rod is sealed -by a suitablesealing gland.- The rod 30 carries Va collar or body 72 at its upperend, Iand is biased to valve-closed position by a spring 31 actingbetween the `cover 28 and the body 72. As indicated in FIG. 5, the coverplate 28 is fixed to the rectangular mounting plate 26 by a pair ofsocket-head bolts 32 at opposite corners of the rectangular plate. Theother pair of opposite corners is adapted to receive hex-head stud bolts34 for mounting on the valve bod-y the casing 40 of the valve-operatingmechanism. As indicated in FIG. 6, this 'casing 40 comprises top,bottom, and end walls forming an open body `of rectangular crosssection. This is. adapted to` be closed by -a front 'or handle coverplate 44 and a rear or access cover plate 46. Partition walls 48 and 49form an electric junction box within the casing 40, and this is closedby the upper part of the rear cover plate 46. An opening in the bottomwall 49 of the junction box l) permits electrical connection to thevalve operating mechanism, and an opening in the end wall of thejunction box 50 provides yfor connection to an electric conduit.

The central portion of the front cover plate 44 carries a sleeve S2 inwhich is journalled `a manual operating arm 54, sealed by `an O-ring 53.This carries a dial indicator 56 having a rearwardly projecting stopange 58 over approximately 180 degrees of its circumference, and suchflange cooperates with a -xed stop 60 formed on the cover plate `44 tolimit the Imovement of the manual operating arm 54 to 180 degrees ofthrow. The rear end of the operating arm 54 carries a crank 62 having -acrank pin 64for operating the valve. This is connected by a link 66 tolan intermediate point on a lever 68. Such lever is conveniently formedfrom a pair of curved side plates 69 held in spaced relation by aplurality of rivets and spacers along its length. The left end of thelever 68 as shown in FIGS. l and 2 is connected by -a pin 70 to thevalve operating body '72 fixed to the upper end 'of the valve operatingrod 30. The opposite end of the lever 68 carries a roller 74 whichnormally rests on the top surface of a fulcrurn stand when .the deviceis in latched valve-operating condition.

When the fulcrum support comprising the stool 76 is in operativeposition Aas shown in lfull lines in FIGS. 1 and 2, the valve 22 can beopened and closed at will by operation `of the handle 55. Moving suchhandle counterclockwise from its position in FIG. l causes the crank 62,acting through the link 66, to tilt the lever xabout its fulcrum roller74, and this depresses the valve rod 30 to valve-open position as shownin FIG, 2. The crank pin `64. moves past dead center as ,the handlekends its movement, andthe valve is then locked in open position.Reverse movement of the handle 55, clockwise from the position of FIG.2, will return the lever .to its position in FIG. l and allow `the valveto close.

The fulcrum support shown in the drawings comprises the Aulcrum stool 76pivotedby a pin 78 on a rocker or bell crank 89. The -bell crank 80(FIGS. 3 and 4) has a pair of side plates 84 and S6 interconnected bythe pivot pin 78 and by two spacing rivets 88 and 89, and ispivot-allymounted on a lixed pin 82` between :two bosses on the casing40. The stool 76 is held counter-clockwise against the pin 89 as a stop,-by means of a spring S1. One side plate 86 of the bellcrank extendslaterally to support a yoke 90 having a slotted upper end which engagesa pin 92 carried by an armature 94 of an electromagnetic device 96.

The fixed pin 82 supporting the rocker 80 and the fnlcrum stool 76 liesa substantial distance below the point engaged by the lever roller 74,generally in the direction of the line of `force exerted by the rolleron the fulcrurn stool, `and offset inwardly from that line of force.Further, the upper face of the fulcrum stool engaging the roller 74 hasa slope such that the interengagement tends to pivot fthe fulcrurn stool76 counter-clockwise toward vits stop 89 and tends tto pivot thecombined rocker 80 and stool 76 as a unit clockwise away from its leversupporting position. To this end, the slope is such that aline normal tothe face at the point of roller engagement will lpass between the axesof :the two pins 7-8 and 82. For this purpose, ythe roller engaging faceof the fulcrum stool 78 desirably lies on an arc of radius R about a-point C between the centers of the stool pin 78 and the rocker -pin 82.As a result, Ithe -fulcrum support 76-80 is unstable in the full lineposition of FIGS. 1 and 2, and tends to pivot clockwise to the positionshown in FIG. 3. Any pressure of the fulcrum roller 74 on the fulcrumstool 76 tends to cause the bell crank to pivot in such direction. Thiswill carry the fulcrurn stool 76 out from under the fulcrum roller 74and destroy the support for such roller 74 and for the norm-allyfulcrumed end of the lever 68.

Accordingly, the fulcrurn support 76-80 is capable of supporting thefulcrum roller 74 only when the bell crank is held in itscounterclockwise position by the electro`d magnetic device 96 actuatedby the energization of the controlling electric circuit. When theelectric circuit of the magnetic device 96 is not energized, the fulcrum`support 76-80 will not support the lever, and it will be impossible toopen the valve from its closed position to its open position. Instead,as indicated in FiG. 3, any attempt to actuate the lever by manipulationof the manual operating rod 54 will simply swing the lever 63 freelyabout the pin 78 by which it is connected :to the valve `operating body72, and the mechanism will be incapable of overcoming the bias of thebiasing spring 31 which holds the valve 2G in closed position.

When the electromagnetic device is energized, however, its armature 94will pull the bell crank to its counterclockwise position as shown infull lines in FGS. yl and 2, the iulcrum stool 76 Will move to itslatching position as shown in FIG. l, where it will be in position tounderlie the fulcrum roller 74, but will be retractable clockwise (FIG.2) against its spring 8l to pass the roller 74 from its dotted lineposition in FIG. 2 to its full-line position in FIG. l. Placement of themanual operating arm 54 in its Latch position (FIG. l) will dispose thelever 68 in its raised position, with its fulcrum roller 74 overlyingthe fulcrurn stool 76, and subsequent movement of the lever to its Openposition (FIG. 2) wil-l be citeetive to move the valve from closed toopen position as has been described. With the valve held in openpcsition bythe lever and with the parts in the position shown in fulllines in FIG. 2, if the electrical circuit becomes deenergized for anyreason, the bell crank or rocker Si) will be released for clockwiseypivotal movement under the influence of the force exerted on the fulcrumstool 76 by the fulcrum roller 74. Such clockwise movement of the bellcrank will carry the fulcrum stool 76 out from under the fulcrum roller74 .and remove the fulcrurn supe port for the lever 68, leaving it freeto swing about its point of connection to the operating link 66 to theposition shown in dotted lines in FIG. 2. This will permit the spring 31to move the valve-operating rod 38 from its valve-open position shown infu-ll lines in FIG. 2 to its valve-closed position shown in -dottedlines in PEG. 2 and in full lines in FIG. l. Accordingly, the valveactuating mechanism will automatically release the valve to closedposition in the event of any failure of the electric circuit energizingthe electromagnet device 96. As long as that electric circuit remainsde-energized, it will be impossible to re-open the valve, for thefulcrum stool will be in nonsupporting position as shown in FIG. 3, andany operation of the manual operating arm 54 will merely cause the lever68 to swing freely about the pin 70 and not to actuate the valve rod 36.

The end Wall 41 of the casing 40 carries a window 100 behind which aplate 102 carries a suitable legend such as the word Shut indicatingthat the valve is closed. Such plate 102 is spaced behind the window topermit a curtain plate 164 carried with the valve operating rod 39 todrop -from its full line position of FIG. l to its lowered position ofFIG. 2 in front of the plate 162. Such curtain plate 104 will cover thelegend Shut and will carry on its front face a suitable legendindicating that the valve is open, for example, `the word Open Thelegend exposed through the window 106i will indicate directly whetherthe valve operating stem 30 is in open or shut position. It is of coursedesirable to have this visual indication since the fact that the manualoperating arm S4 is in open position :does not necessarily indicate thatthe valve is open, for the valve may be closed, as shown in dotted linesin FG. 2, by reason of the failure of the electrical circuit energizingthe magnetic device 96.

Conveniently, the curtain wall 1M carries a laterally projecting arm 106which in raised position actuates the arm ltt of a switch llt? which maybe connected to a remote signal device to indicate the condition of thevalve.

We claim as our invention:

l. A device lfor operating a valve, comprising (a) an operating membermovable between first and second positions Iand biased to its saidsecond position,

(b) a lever pivotally interconnected at an operating point with saidoperating member and having a fulcrum point spaced from said operatingpoint,

(c) an actuating member interconnected with said lever at an actuatingpoint spaced from said operating and fulcrum points,

(d) said actuating member being operable, in the presence of support forsaid fulcrum point, to pivot said lever thereabout for moving saidoperating member to its said first position, and in the absence of suchsupport, to swing said lever about its operating point ofinterconnection with said actuating member,

(e) a fulcrum support having a lever-supporting position in which thefulcrum point of said lever is supported .thereon and exerts thereon aforce in a predetermined line,

(f) means for mounting said fulcrum support on a fixed axis transverseto said line,

(g) said fulcrum support being movable about said axis, in apredetermined direction relative to said line, to a non-supportingposition clear of said lever,

t l1) said iixed axis being spaced a relatively substantial distancealong said predetermined line from said fulcrum point and being offset arelatively small distance from said line in a direction opposite to saiddirection of fulcrum support movement, the position of said fixed axisbeing such that the lever force on the fulcrum support has a relativelylarge major component in the direction of said fixed pivot axis fortransmitting substantially the entire lever force directly to said fixedaxis and has a relatively small minor component in said predetermineddirection tending to pivot said fulcrum support from its leversupportingposition to its lever-clearing position,

(i) and electromagnetic means operatively connected to said fulcrumsupport and operable, when energized, to retain said fulcrum support inits said lever-supporting position.

2. A device for operating `a valve as defined in claim l,

further comprising (a) a roller on one and a roller-engaging face on theother of said fulcrum support and said lever at its said fulcrum point,

(b) said roller-engaging face being sloped to recede in the direction ofrelative movement of the roller thereover during pivotal movement of thefulcrum support from lever-supporting to lever-clearing position.

3. A device for operating a valve as defined in claim l in which (n)said xed axis is positioned along said predetermined force line in thedirection of lever force on said fulcrum support,

(b) and said fulcrum support forms a strut stressed in compressionbetween said lever fulcrum point and said iixed axis.

4. A device for operating a valve as defined in claim 1 in which (a) oneof said operating and actuating members is confined to linear movementin a predetermined path and said lever is pivoted thereto to tix thelengthwise position of the lever in its angular lever movements,

(b) and the fulcrum support supports lthe fulcrum point of the lever formovement thereon lengthwise o-f the lever during angular lever movementabout the supported fulcrum point.

5. A device for operating a valve, comprising (a) an operating membermovable between irst and second positions and biased to its said secondposition,

(b) a lever pivotally interconnected at an operating point with saidoperating member and having a fulcrum point spaced from said operatingpoint,

(c) an actuating member interconnected with said lever at an actuatingpoint spaced from sai-d operating and fulcrum points,

(d) said actuating member being operable, in the presence of support forsaid fulcrum point, to pivot said lever thereabout for moving saidoperating member to its said first position, and in the absence of suchsupport, to swing said lever about its operating point ofinterconnection with said actuating member,

(e) a fulcrum support having a lever-supporting position in which the-tulcrum point of said lever is supported thereon and exerts thereon aforce in a predetermined line,

(f) said fulcrum support, in said lever-supporting position, forming astrut stressed in compression between said lever and a iixed pointspaced a substantial distance along said predetermined line in thedirection of lever force on said fulcrum support,

(g) said strut being inherently unstable in said leversupportingposition, and in the absence of retention therein being incapable ofsupporting the lever,

(h) and electromagnetic means having an armature connected to controlsaid strut and operative when energized to retain said strut inlever-supporting position.

6. A device for operating a valve, comprising (a) an operating membermovable between first and second positions and biased to its said secondposition,

(tb) a lever pivotally interconnected at an operating point with saidoperating member and having a fulcrum point spaced from said operatingpoint,

(c) an actuating member interconnected with said lever at an actuatingpoint spaced -from said operating and fulcrum points,

(d) said actuating member being operable, in the presence of support forsaid fulcrum point, to pivot said lever thereabout for moving saidoperating member to its said iirst position, and in the absence of suchsupport, to swing said lever about its operating point ofinterconnection with said actuating member,

(e) a roller on said lever at said fulcrum point,

() a fulcrum support having a roller-engaging face for supporting saidroller in fulcrum position,

(g) and structural means supporting said face from a pivot axis spacedin the direction of and oiset from a line normal to said .face at itspoint of engagement by said roller,

(h) said fulcrum support being pivotally movable about said axis in apredetermined direction to carry said face out of supporting relationwith lsaid roller,

(i) said face being sloped to recede in the direction of relativemovement of the roller thereover during such pivotal movement of thefulcrum support, whereby roller force on said face tends to move thefulcrum support to non-supporting position,

(j) and electromagnetic means which in energized state exerts tractionon said fulcrum support to maintain said face in roller-supportingposition.

7. A device for operating a valve, comprising (a) an operating membermovable between -tirst and second positions and biased to its saidsecond position,

(b) .a lever pivotally interconnected at an operating 7 point with saidoperating member and having a fulcrum point spaced from said operatingpoint,

(c) an actuating member interconnected with said lever at an actuatingpoint spaced from said operating and fulcrum points,

(d) said actuating member being operable, in the presence of support forsaid ulcrum point, to pivot said lever thereabout for moving saidoperating member to its said rst position, and in the absence of suchsupport, to swing said lever about its operating point ofinterconnection with said actuating member,

(e) a fulcrum support for said lever, comprising `a stool having alever-supporting platform, a rocker member mounted on a rocker pivotaxis and supporting said stool on a stool pivot axis, and a stop on saidrocker against which Said stool is biased in a normal lever-supportingposition,

(f) said rocker pivot axis being spaced from said platform in thedirection of and offset from the line of force exerted by the lever onthe platform, said rocker-pivot axis being thereby positioned so thatsaid rocker, under the inuence of said force, tends to rock in adirection to carry the stool away from lever-supporting position andrelease the fulcrum point of the lever for free swinging movement,

(g) and an electromagnetic device which in energized state exertstraction on said rocker to move the same to and maintain it in aposition supporting the stool in lever-supporting position.

8. A device for operating a valve, comprising (a) an operating membermovable between first and second positions and biased to its said secondposition,

(b) a lever pivotally interconnected at an operating point with saidoperating member and having a fulcrum point spaced'from said operatingpoint,

(c) an actuating member interconnected with said lever at an actuatingpoint spaced from said operating and fulcrum points,

(d) said actuating member being operable, in the presence of support forsaid fulcrum point, to pivot said lever thereabout for moving saidoperating member to its said first position,

(e) a fuicrum support for lsaid lever, comprising a stooi pivotallymounted on a iirst axis on a rocker mounted on a iixed second axis,`

(f) said stool being biased to a stop position on said rocker,

(g) said stool having a lever-supporting face and said axes. being oisetin opposite directions from a line normal to said face at its point oflever support,

(It) said face being sloped to rise relative to the lever fulcrum pointon movement of the stool away from its stop position about said iirstaxis and torecede relative thereto on movement of the stool and rockerin the saine direction about said second axis, whereby the lever forceon said face tends to bias said stool toward its stop position and tobias said rocker and stool assembly toward movement in said directionaway from lever-supporting position,

(i) and means for releasabiy maintaining said rocker in itslever-supporting position.

9. A device for operating a valve as defined in claim 8, in which (a)said face lies in'an arc about a point between said fjrst and secondaxes.

l0. A device for operating a valve, comprising,

(a) an operating member movable between rst and second positions andbiased to its said second position,

(13) a lever pivotally interconnected at an operating point with saidoperating member and having a fulcrurn point spaced from said operatingpoint,

(c) an actuating member interconnected with said lever at an actuatingpoint spaced from said operating and fulcrum points,

(d) said actuating member being operable, in the absence of support forsaid fulcrum point, to swing said lever about its operating point, tocarry its fulcrum point in an arcuate path thereabout, the operatingpoint being positioned by the operating member in its said secondposition,

(e) a fulcrum support comprising a rocker member mounted on a faredpivot axis outside said arcuate path, and a fnlcrum stool pivotallymounted on said rocker member and biased toward said path to a stopposition on said rocker,

(f) said rocker having an operative position in which it disposes saidstool generally tangent to said arcuate path and with a portion thereofin said path to support the lever iulcrum point in fulcrum position,

(g) said actuating member, in the presence of said lever tulcrumsupport, being operable to move said operating member to its said iirstposition,

(lz) said rocker being unstable in said operative position and tending,under lever force, to move to an inoperative position in which itdisposes said stool portion outside the arcuate path of said ulcrumpoint,

(i) and electromagnetic means which in energized state exerts tractionto move said rocker to and retain the same in its operative position,

(j) said stool being yieldingly retractable about its pivot axis on saidrocker to pass said lever fulcrum point to ulcrurn position.

References Cited in the tile of this patent UNITED STATES PATENTS2,301,876 Hurlburt Nov. l0, 1942 2,839,929 Hurlburt June 24, 19582,875,616 Marks Mar. 3, 1959

1. A DEVICE FOR OPERATING A VALVE, COMPRISING (A) AN OPERATING MEMBERMOVABLE BETWEEN FIRST AND SECOND POSITIONS AND BIASED TO ITS SAID SECONDPOSITION, (B) A LEVER PIVOTALLY INTERCONNECTED AT AN OPERATING POINTWITH SAID OPERATING MEMBER AND HAVING A FULCRUM POINT SPACED FROM SAIDOPERATING POINT, (C) AN ACTUATING MEMBER INTERCONNECTED WITH SAID LEVERAT AN ACTUATING POINT SPACED FROM SAID OPERATING AND FULCRUM POINTS, (D)SAID ACTUATING MEMBER BEING OPERABLE, IN THE PRESENCE OF SUPPORT FORSAID FULCRUM POINT, TO PIVOT SAID LEVER THEREABOUT FOR MOVING SAIDOPERATING MEMBER TO ITS SAID FIRST POSITION, AND IN THE ABSENCE OF SUCHSUPPORT, TO SWING SAID LEVER ABOUT ITS OPERATING POINT OFINTERCONNECTION WITH SAID ACTUATING MEMBER, (E) A FULCRUM SUPPORT HAVINGA LEVER-SUPPORTING POSITION IN WHICH THE FULCRUM POINT OF SAID LEVER ISSUPPORTED THEREON AND EXERTS THEREON A FORCE IN A PREDETERMINED LINE,(F) MEANS FOR MOUNTING SAID FULCRUM SUPPORT ON A FIXED AXIS TRANSVERSETO SAID LINE, (G) SAID FULCRUM SUPPORT BEING MOVABLE ABOUT SAID AXIS, INA PREDETERMINED DIRECTION RELATIVE TO SAID LINE, TO A NON-SUPPORTINGPOSITION CLEAR OF SAID LEVER, (H) SAID FIXED AXIS BEING SPACED ARELATIVELY SUBSTANTIAL DISTANCE ALONG SAID PREDETERMINED LINE FROM SAIDFULCRUM POINT AND BEING OFFSET A RELATIVELY SMALL DISTANCE FROM SAIDLINE IN A DIRECTION OPPOSITE TO SAID DIRECTION OF FULCRUM SUPPORTMOVEMENT, THE POSITION OF SAID FIXED AXIS BEING SUCH THAT THE LEVERFORCE ON THE FULCRUM SUPPORT HAS A RELATIVELY LARGE MAJOR COMPONENT INTHE DIRECTION OF SAID FIXED PIVOT AXIS FOR TRANSMITTING SUBSTANTIALLYTHE ENTIRE LEVER FORCE DIRECTLY TO SAID FIXED AXIS AND HAS A RELATIVELYSMALL MINOR COMPONENT IN SAID PREDETERMINED DIRECTION TENDING TO PIVOTSAID FULCRUM SUPPORT FROM ITS LEVERSUPPORTING POSITION TO ITSLEVER-CLEARING POSITION, (I) AND ELECTROMAGNETIC MEANS OPERATIVELYCONNECTED TO SAID FULCRUM SUPPORT AND OPERABLE, WHEN ENERGIZED, TORETAIN SAID FULCRUM SUPPORT IN ITS SAID LEVER-SUPPORTING POSITION.